The present invention relates to the control of regenerative braking in a motor vehicle.
More specifically, the subject of the invention is a method for controlling the regenerative braking of a vehicle equipped with a combustion engine and/or with at least one electric motor.
This invention finds applications in any motor vehicle equipped with at least one electric motor and with associated storage means, notably batteries, whether this be a strictly electric vehicle, or hybrid vehicle that comprises a combustion engine associated with at least one electrical machine.
The regenerative braking function is generally decoupled from the vehicle brake pedal. In such cases, the power train (GMP) control system controls the braking effort applied to the wheels by the brake pads to optimize recuperation of energy. Thus, when the driver depresses the brake pedal, the GMP control unit may go so far as to cancel the effort to be applied via the pads (no dissipation of kinetic energy) so as to maximize the recuperation of energy by the electric motor(s).
Publication FR 2 230 515 describes such a system, in which the level of regenerative braking is connected to the extent to which the brake pedal is depressed. More specifically, it is the strength of the current that provides the regenerative braking that is directly dependent on the position of the brake pedal, without taking the condition of the vehicle (speed, battery charge level, etc) into consideration. Now, it may be desirable to alter the recharging current under certain circumstances, particularly when the battery is already at a high level of charge, to avoid damaging it.
Publication US20020030408 describes another method of controlling the regenerative braking of a vehicle, which is modulated according to the braking demand from the driver, and of a balance ratio between front and rear axle assemblies. The conventional braking system is, however, decoupled from this control, thereby increasing the cost of the system. In addition, the way in which the regenerative braking setpoint is calculated does not take account of any engine braking that causes the vehicle to decelerate with the foot off the pedal, and this may lead to discontinuities in the deceleration when switching from a braking phase to a foot-off phase. Drivability can suffer under such conditions.
To sum up, the known methods are unable to optimize electrical energy management in the vehicle and therefore minimize fuel consumption, in the case of a hybrid vehicle, or maximize range in the case of electric vehicles.